baldymcgee6
Partial Derivatives... posted below



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baldymcgee6
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dw:1351748975295:dw

hartnn
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partial derivative means u treat other variable as constant.
u know this ?

baldymcgee6
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Right, so we treat y as a constant in the first one..

Dido525
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Which variable are you taking constant>?

hartnn
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yes.

baldymcgee6
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dw:1351749134665:dw

hartnn
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absolutely!
that was my next statement, that u need log diff. here.

baldymcgee6
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In my experiences with log diff I always had a function in the form of y = f(x)^g(x).... So what do we do here?

baldymcgee6
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do we write y = ......?

hartnn
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taking log on both sides, u get
log y = g(x) log f(x)
then use product rule

hartnn
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u'll also need a chain rule for this....

baldymcgee6
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dw:1351749340629:dw

hartnn
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oh dear! the y on left and on right are different, u should have used g or some other letter

baldymcgee6
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oohhhhhh.. that's where I went wrong... this is off my last quiz :/

baldymcgee6
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so it'll be g'/g on the left?

hartnn
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yes, after doing product rule , u resubstitute for g

baldymcgee6
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dw:1351749800366:dw

hartnn
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thats right

baldymcgee6
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dw:1351749846652:dw

hartnn
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absolutely correct

hartnn
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same for 2nd question, just replace x with y and y with x

baldymcgee6
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right... I just messed up on calling the function y... messed with my head.

baldymcgee6
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thanks again for the insight!

baldymcgee6
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I'm not going to do the second derivative, I think I can get it... Thanks so much!

baldymcgee6
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I mean, i'm not going to do it on here.. :)

hartnn
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ok, welcome ^_^